In the 3GPP specification, the radio link control (RLC) protocol layer is responsible for the delivery of protocol data units (PDUs) over the radio interface. An acknowledge mode may be used to ensure reliable delivery of a PDU. In this mode, the receiver sends a status report indicating the successful reception of a PDU. It is known to include a polling bit in the RLC PDU header to trigger a status report from the receiver indicating that PDU have been received. In another solution, the RLC PDU header may not include a polling bit but a status report is instead triggered by a separate polling control unit sent to the receiver.
In some wireless communication protocols, it has been suggested that the RLC layer re-segment a PDU if it has not been received successfully after the initial transmission. When retransmitting the same PDU, the entire PDU may be transmitted in individual segments, also know as re-segmented PDU segments. For example, an original PDU of size 1000 bytes can be re-segmented into three PDU segments of size 350 bytes, 400 bytes and 250 bytes. Three segments is an arbitrary number and only used as an example. For the newly generated PDU segments, status report is needed after the transmission. Further, it is beneficial for the sender of the PDU to know the status of the PDU reception so that the transmission window can be advanced and the receiver buffer can be freed up for new data. One approach would be to include a polling bit in the data unit being re-segmented. However, in case of some RLC protocols, it might be inefficient to include a polling bit in every data unit being transmitted, where the bit value is toggled between indication that a status report is required or not. Furthermore, due to the overall configuration of the protocol, a poll prohibit timer may be running and as a consequence prevent the setting of the poll bit. Alternatively the status prohibit timer may be running and thereby prevent the transmission of the status report. However, there is significant benefit in receiving a status report as soon as the last segment of the re-segmented data unit has been received. For instance, in some cases this may allow the sender to advance the transmission window, there by allowing further packet transmission to the receiver and thus ultimately improving the user experience. Thus it would be beneficial to identify an efficient mechanism to trigger a status report following transmission of the re-segmented PDU.
The various aspects, features and advantages of the disclosure will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description thereof with accompanying drawings described below. The drawings may have been simplified for clarity and are not necessarily drawn to scale.